Description.
The TV transmitter circuit given here uses UK standard 1 FM modulation for sound and PAL for video modulation. The audio signal to be modulated is pre-amplified using the transistor Q1 and associated components. The transistor Q2 has two jobs: production of carrier frequency and modulation. The pre-amplified audio signal is fed to the base of transistor Q2 for modulation. Capacitor C5 and inductor L1 forms the tank circuit which is responsible for producing the carrier frequency. The video signal is fed to the emitter of transistor Q2 via POT R7 for modulation. The modulated composite signal (audio+video) is transmitted by the antenna A1. This TV transmitter circuit can be operated from 12V DC. Either a 12V DC power supply or a battery can be used for the purpose, using a battery will surely reduce noise and improve the performance. If you are going with a DC power supply, then it must be well regulated and free of noise.

Circuit diagram with Parts list.

Notes.

Assemble the circuit on a good quality PCB.

Inductor L1 can be made by making 4 turns of 24SWG enameled copper wire on a 6mm dia: plastic former.

T1 can be a radio frequency transformer with built in capacitor. (Can be found on old transistor radio boards).

Antenna A1 can be a 1M long copper wire. (Experiment with the length to get optimum performance).

This transmitter is working in VHF band somewhat between 50 – 210MHz.

This transmitter is compatible only with PAL B and PAL G systems.

Slight adjustments are required on the value of C8 for getting optimum performance.

Comments

Setharaman Jee, I am trying to make an UHF tv transmitter for which I have already found the circuit for video & it is working. Now for audio can I use the audio portion of your circuit i.e. upto c4 for the UHF transmitter? Also do I need any re-arrangement of circuit etc. Please reply me at your convenient. Thanks. This is the second time I am approaching you. Please reply.

It’s very important to say: T1 iz transformer, of course, primar side of this transformer is LC circuit and must be set on 4.5 – 6.5 MHz (for PAL its 5.5 MHz, for Secam its 6.5 MHz etc.). Primary side must be made from one coil and one capacitor, not just coil like on schematic. The frequency of thic LC circuit can be calculated by Thompson equation. f=1/(2*Pi*SQRT(L*C)). L is in Henry and C in Farad of course.Second side of this transformer just transforms voltage. If you make this circuit like is on this schematic there will be problem with sound. First part of schematic is oscilattor which must oscillate on some frequency (5.5 MHz for PAL).

Setharaman Jee, I am trying to make an UHF tv transmitter for which I have already found the circuit for video. Now for audio can I use the audio portion of your circuit i.e. upto c4 for the UHF transmitter? Also do I need any trimming etc. Please reply me at your convenient. Thanks.

This is realy a cool site to me, Many thanks to the initiators of Circuit to day. This site can greatly improve and enable any student or researcher in the field of communication to be able to explore electronics communications to the depth. GOD bless you sir/ madam.

ABOUT WORKING: Normally we connect one end of tank circuit(in this case collpits oscillator) directly to base of the BJT for providing positive feedback but here it has been connected to emitter . The reason is that at VHF frequency the base emitter capacitance,Cje, will act as short circuit. So it is equivalent to connecting directly to base.

Hi Saad Please see reply dated 5th Jan 2014 of Mr. Prince.
Hi Muhammad CATV amplifier are for boosting the signal in cable TV to 1volt pk signal. you can not use it as an RF amplifier to drive an antenna for which you require a RF power amplifier.

Ensure the web cam is capable 1 volt pk video information if less add a suitable amplifier between camera and video input. you can use a carbon micro phone with suitable pre amplifier to produce an audio input of at least 1volt at the audio input socket.

Dear Seetharaman, I want your help in making Automatic Room Light using AT89C51 Microcontroller. I assembled the circuit based on two ir sensor, two ic 555 and two visitor counters. Every parts is ok but the circuit is not working. I do not know how to use source code. I never worked with microcontroller. But I want to make Automatic Room Light controller. Can you help in this regard please! With thanks!

Hi all,
Who built this circuit?
Which parts of the circuit should be changed to optimize the output?
To increase the frequency to 500 MHz, what parts should be replaced and what elements should be?
Please answer.
Thank you very much

I realized the circuit but got very poor results. I would suggest you to try some different circuit or maybe purchase a RF converter kit and do reverse engineering.This circuit will not give optimum results without a RF amplifier{not tested).Anyway why go in UHF range? it will only complicate matters of impedance matching and antenna interfacing.And if you are short on time(I was), purchase a wireless camera online at robokits.co.in.

Dear Umakant, I have not enough knowledge in electronics. But I will definitely tell you what I did in this project. I simply made this circuit without audio as given above because I did not find T1 (IFT) so I connect the simple FM Transmitter with it. But still I did not test it with audio but the transmitted video is very clear. I removed the trimmer C5 and using the fm gang condenser to tune it easily. And, I took the copper wire from the cable TV coming out from the house and wind it four turn on telescopic antenna of the codeless phone. I also changed R5, R6 with 1K and using Nokia cell phone charger. I hope this will help you. I am sorry for the poor English.

Hi Umakant L1 is self supporting air core coil. you can wind it on a pencil slide out and use it. the windings are close wound. latter for tuning you can expand the winding little(small gap between each winding). C5 you can use oscillator section of PVC2X.(around 45PF) C8 can be anything between 2.2 to 27PF. Alternately you can connect Antenna directly to L1 tap at 1/2 turn from supply end.

Dear Seetharaman, I build this TV transmitter circuit. But the video is not stable and the screen goes up and down. I tried to control it using the V-hold control of my TV but the result is same. Please help to solve this problem. And also please tell me how I can increase its video quality. With thanks in advance!

Dear Virender First check your power supply is of good quality with least ripple. if your power pack is ok, you may be over modulating, you may correct it by adjusting the video modulation control R7. This should solve your problem.

hello sir,
i like to make this but i know more…
so, plz tell what transformer (t1) needed for this sellers ask for what transformer what is that tranformer if cannot buy it in marcket plz tell me what can i use for it?

I just released this circuit but audio part is not running, advice me what to do because i lost required frequency transformer, can i released other audio circuit and combine them after? if ok, tell me how to find that circuit. Thx!!!! still waiting ur best answer

hi! i already released this circuit but is not running i thing the problem is final oscillator capacitor and coil if possible sent to me images of coil to be used is it air follow or it has other material inside? plse help me

Hi Hi!!!!! In my country is not illegal, so advice me amplifier to use by sending precise link where i can find it because sent link i find many and i miss how to choose which one is compatible, is helpful i you send a full circuit i can use, thanks

Hi Sylvain you have to use high power RF Transistor in class C mode with tank and aerial tuning unit after Q2 and tune it with SWR meter etc. it is not under the purview of this article. you require licence etc.

Tell me more about amplifier, can i use audio amplifier of 30watts made with TDA2040 with frequency limit of 100khz you presented in audio amplifier? pleas help me i need to implement this 10km tv transmitter, thanks!

what are the requirements to release the circuit said to operate up to 10km? any modification to the circuit presented or only addition tunable amplifier is added? transistor used are BC547 or 2N2219? whit type of antenna used to this circuit?

hello sir
i want to make a video transmitter circuit and a receiver for my project would u help me in giving the basic idea and how to proceed..?
sir
basically i want to know everything of each component so please send me data sheets or ref sites
thank u sir

hello sir
i want to make a video transmitter circuit and a receiver for my project would u help me in giving the basic idea and how to proceed..?
sir
basically i want to know everything of each component so please send me data sheets or ref sites
thank u sir

hello seetharaman…. first of all i am a fan of u and of circuitstoday…no better website than this for hobby projects….main thing is u people are responsive to requests and i also u dont steal circuits and post them blindly but you work them out,and study them before posting,u are doing a real great work.

i would like to know that if it is possible to transmit comp usb data via any digital modulator circuit over the air and get it received by demodulator…i dont ask for any high speed lan type of performance but even simple hyperterminal would do…or maybe atleast ability to transfer data between two pcs but by our own made diy circuit…and how much challenging it would be..
thankyou
hb

HI Seetharaman THANKS
Can eplanin me more about,ceramic capacitor disc,UF ,PF,N i dont know which is big size,or big voltage,,,i see ceranic disc have 3 kind color ,,red .green.blu..same example here,B103K, B472K.B181,,151J,,681J.,i cant understand about this,how i can chack part is good or bed,what kind multimeter,can chack,ceramic disc.
I dont know for size of rasistor,which is big [K] or [OHM] or [M] i need to learn more,i just start to learn.
THANKS

Hi Avdi for ceramic disc capacitors there is no polarity. there metal discs and ceramic insulatotors are stacked alternatly. they are not wound hence no inductive component involved,due to which they are most suitable for high frequency circuits. but they are available in low values upto 2uF votage from 12 to few kV. normally text will be on one side and the other side will be blank. same resistance code type but written in numerals. say 104 means 10 X 10 to the power four PF. 101 means 10 X 10 to the power 1. that is 100PF etc.

i m having difficulty in connecting capacitor “C5” .
This variable capacitor is actually having 3 legs. & in circuit diagram it is shown with 2 legs only . So plz explain me , how to connect these 3 leg capacitor “C5” in the circuit.

i cannot get 2N2219 transister any where.pls advise other same value transister.how create power amplifier with tuned circuits? pls send the circuit diagram.
pls look to circuit as Capsitor 3,11,12.it’s other leg where to be connect? it is free ? or it is earth?

Hi Naseef We are not supposed to radiate signal beyond our compound, beyond this is illegal in most of the countries.
By increasing power you can achieve better range, less noise and better clarity.
By increasing frequency nothing can happen to range.
A vertical whip antenna is to be of one forth the wavelength. This is antenna theory a small fine tuning is required to improve the radiated power.
You can also use two folded dipoles one above other at right angle with the transmitter, To have a coverage of figure of eight.

sir,
thanks,
1.when i rise circuit frequency to wide area,will get full clarity in vedio and audio?
2.how much KM distance we can rise maximum?
3.any illegal problems for the TV transmitter by POlice or Govt

Hi Daniel you can use any PAL set you can tune the oscillator to cover old turret tuner’s Ch 2 to Ch 12. Band I ch 2 to 4
and Band III ch 5 to 12. T1 can be SW 5 pin oscillator coil or old sound card input transformer 5.5MHz or FM IFT with additional capacitor to tune to 5.5MHz.

John! In old transistor radio board I found there are couple of T1 type radio frequency transformer. Could you specify which one of them, red, yellow, white, as these IFT transformer have different capacitor value

Hi Rajesh use a pocket FM radio with TV sound to check the frequency, or directly connecting it to your tv and search tuning it and get the frequency.
Hi Govind Chinese make simple pin hole camera without flash for 35mm film is available for less than IR100.00 in the market. Tell me your specs. i will advice.
Hi Raj you can use Solar photo voltaic cells, wind power generator, hand crank generator(have you seen the latest philips LED torch light with hand crank charger-environment friendly). You may fit dynamos to all these fintness centres, the human energy wasted there can be utilised in a better way – hey not joking i am serious about it – do you remember GD Naidu has done it for watering his garden)
Hi Farrukh the video input can be from you vcd player or from video camera or from any video source. any tv set can be used.

Dear Murugan you can use any camera with an analog video out put signal of around 1 volt peak. lighting level for the object and modulation level pot R7 you have to adjust to suit your requirement. Best wishes

July 9th, 2009 at 8:07 am
all these components are not common in Ghana, so how can i get some?

Hi Desmond

Email these two companies and ask if they will ship to Ghana from the UK.rapidonline.com
uk.farnell.com
I think you will be plesently surprised.
As a suggestion, have you tried looking in old TV’s and radio’s?